Calcitriol

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C₂₇H₄₄O₃     416.64 

C₂₇H₄₄O₃.H₂O     434.65  

9,10-Secocholesta-5,7,10(19)-triene-1,3,25-triol, (1α,3β,5Z,7E)-; 

(5Z,7E)-9,10-Secocholesta-5,7,10(19)-triene-1α,3β,25-triol CAS RN®: 32222-06-3. Monohydrate CAS RN®: 77326-95-5

1 DEFINITION

Calcitriol is anhydrous or contains 1 molecule of hydration. The anhydrous form contains NLT 97.0% and NMT 103.0% of calcitriol (C₂₇H₄₄O₃),

calculated on the solvent-free basis. The monohydrate form contains NLT 97.0% and NMT 103.0% of calcitriol (C₂₇H₄₄O₃), calculated on the 27  

anhydrous basis. 

[Caution—Care should be taken to prevent inhaling particles of calcitriol, and exposing the skin to it.] 

2 IDENTIFICATION 

Change to read: 

A. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197A or 197K  

B. The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the Assay. 

3 ASSAY 

Procedure 

Carry out the procedure as rapidly as possible, and protect all solutions containing calcitriol from light. 

Buffer: 1.0 mg/mL of tris(hydroxymethyl)aminomethane in water, adjusted with phosphoric acid to a pH of 7.0–7.5 before nal dilution Mobile phase: Acetonitrile and Buffer (55:45) 

Standard solution: 0.1 mg/mL of USP Calcitriol RS prepared as follows. Transfer an appropriate amount of USP Calcitriol RS to a suitable volumetric flask, dissolve in acetonitrile, using 55% of the nal volume, then dilute with Buffer to volume. 

System suitability solution: Heat 2.0 mL of the Standard solution at 80° for 30 min. 

Sample solution: 0.1 mg/mL of Calcitriol prepared as follows. Transfer an appropriate amount of Calcitriol to a suitable volumetric flask, dissolve in acetonitrile, using 55% of the nal volume, then dilute with Buffer to volume. 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 230 nm 

Column: 4.6-mm × 25-cm; 5-µm packing L7 

Column temperature: 40° 

Flow rate: 1 mL/min 

Injection volume: 50 µL 

Run time: NLT 2 times the retention time of calcitriol 

System suitability 

Samples: Standard solution andSystem suitability solution 

[Note—The relative retention times for pre-calcitriol and calcitriol are 0.9 and 1.0, respectively.] 

Suitability requirements 

Resolution: NLT 3.5 between the pre-calcitriol and calcitriol peaks, System suitability solution 

Relative standard deviation: NMT 1.0%, Standard solution 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of calcitriol (C₂₇H₄₄O₃) in the portion of Calcitriol taken: 

Result = (r_U/r_S) × (C_S/C_U) × 100 

r_U = sum of the peak responses of calcitriol and pre-calcitriol from the Sample solution 

r_S = sum of the peak responses of calcitriol and pre-calcitriol from the Standard solution  

C_S = concentration of USP Calcitriol RS in the Standard solution (mg/mL) 

C_U = concentration of Calcitriol in the Sample solution (mg/mL) 

Acceptance criteria 

Anhydrous form: 97.0%–103.0% on the solvent-free basis 

Monohydrate form: 97.0%–103.0% on the anhydrous basis 

4 IMPURITIES 

Organic Impurities 

Carry out the procedure as rapidly as possible, and protect all solutions containing calcitriol from light. 

Buffer, Mobile phase, System suitability solution, Sample solution, Chromatographic system, and System suitability: Proceed as directed in the Assay. 

Analysis 

Sample: Sample solution 

Calculate the percentage of any individual impurity in the portion of Calcitriol taken: 

Result = (r_U/r_T) × 100  

r_U = peak response of any individual peak other than the main calcitriol peak and the pre-calcitriol peak from the Sample solution 

r_T = sum of all the peak responses from the Sample solution 

Acceptance criteria: See Table 1. The reporting threshold is 0.05%. 

Table 1

^a(6aR,7R,9aR)-11-[(3S,5R)-3,5-Dihydroxy-2-methylcyclohex-1-enyl]-7-[(R)-6-hydroxy-6-methylheptan-2-yl]-6a-methyl-2-phenyl 4a,5,6,6a,7,8,9,9a-octahydrocyclopenta[f][1,2,4]triazolo[1,2-a]cinnoline-1,3(2H,11H)-dione. 

^b(5E,7E)-9,10-Secocholesta-5,7,10(19)-triene-1α,3β,25-triol. 

^c(5Z,7E)-9,10-Secocholesta-5,7,10(19)-triene-1β,3β,25-triol. 

^d(5Z,7E)-1α,3β-Dihydroxy-17-[(R)-7-hydroxy-7-methyloctan-2-yl]-9,10-secoandrosta-5,7,10(19)-triene. 

5 SPECIFIC TESTS 

Water Determination 〈921〉, Method I, Method Ic: 3.5%–5.5%, where it is labeled as a monohydrate 

6 ADDITIONAL REQUIREMENTS 

Packaging and Storage: Preserve in tight, light-resistant containers. Store as per labeling instructions. 

Labeling: Where it is a monohydrate form, the label indicates. 

USP Reference Standards 〈11〉 

USP Calcitriol RS